From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41097) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZF24O-0001FE-QF for qemu-devel@nongnu.org; Tue, 14 Jul 2015 11:24:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZF24K-0002Jp-NE for qemu-devel@nongnu.org; Tue, 14 Jul 2015 11:24:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53324) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZF24K-0002Ij-HI for qemu-devel@nongnu.org; Tue, 14 Jul 2015 11:24:28 -0400 From: Juan Quintela In-Reply-To: <1434450415-11339-43-git-send-email-dgilbert@redhat.com> (David Alan Gilbert's message of "Tue, 16 Jun 2015 11:26:55 +0100") References: <1434450415-11339-1-git-send-email-dgilbert@redhat.com> <1434450415-11339-43-git-send-email-dgilbert@redhat.com> Date: Tue, 14 Jul 2015 17:24:26 +0200 Message-ID: <87vbdmep91.fsf@neno.neno> MIME-Version: 1.0 Content-Type: text/plain Subject: Re: [Qemu-devel] [PATCH v7 42/42] Inhibit ballooning during postcopy Reply-To: quintela@redhat.com List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert (git)" Cc: aarcange@redhat.com, yamahata@private.email.ne.jp, liang.z.li@intel.com, qemu-devel@nongnu.org, luis@cs.umu.se, amit.shah@redhat.com, pbonzini@redhat.com, david@gibson.dropbear.id.au "Dr. David Alan Gilbert (git)" wrote: > From: "Dr. David Alan Gilbert" > > Postcopy detects accesses to pages that haven't been transferred yet > using userfaultfd, and it causes exceptions on pages that are 'not > present'. > Ballooning also causes pages to be marked as 'not present' when the > guest inflates the balloon. > Potentially a balloon could be inflated to discard pages that are > currently inflight during postcopy and that may be arriving at about > the same time. > > To avoid this confusion, disable ballooning during postcopy. > > When disabled we drop balloon requests from the guest. Since ballooning > is generally initiated by the host, the management system should avoid > initiating any balloon instructions to the guest during migration, > although it's not possible to know how long it would take a guest to > process a request made prior to the start of migration. > > Queueing the requests until after migration would be nice, but is > non-trivial, since the set of inflate/deflate requests have to > be compared with the state of the page to know what the final > outcome is allowed to be. > > Signed-off-by: Dr. David Alan Gilbert Reviewed-by: Juan Quintela